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Modular motor drives can be considered as multi‐agent systems, in which the agents can work together to reach a common goal. One agent in such a modular motor drive consists of only a subset of the machine phases and power electronic converter modules, and is equipped with a dedicated controller. When the dc‐links of the different agents are connected in series to a single voltage source, giving rise to a so‐called stacked polyphase bridges converter, the power electronic converter components can have low voltage ratings. However, a voltage balancing controller must ensure that the total dc‐link voltage is distributed evenly among the agents when working in motoring mode. The goal of this research is to propose a multi‐agent voltage balancing algorithm based on dynamic average consensus, which depends solely on local computations, local measurements, and neighbour‐to‐neighbour communication. The scalability and reliability of the modular hardware are hence extended towards the control. Simulations and experimental results on a 4 kW modular axial‐flux PMSM demonstrate the feasibility of the concept. [ABSTRACT FROM AUTHOR]

A stacked polyphase bridge converter consists of multiple standard, three‐phase two‐level voltage source inverters connected in series to the same dc voltage source. The authors present a decentralised and dynamic dc‐bus reconfiguration strategy for this type of converter. The innovation of the proposed strategy lies in its ability to isolate or reactivate one of the inverters in the series connection online, even in motoring mode, enabling increased fault tolerance and an extended speed range. Both the required hardware alterations and the multi‐agent control strategy are addressed. Its major benefits compared to the state‐of‐the‐art are that only two additional active, unidirectional semiconductor switches are required per inverter, and that the control is based on local computations, local measurements and neighbour‐to‐neighbour communication only. Hence, the scalability and reliability of the hardware are extended towards the control. Simulations and experimental results on a 4 kW modular axial‐flux PMSM prove the feasibility of the concept, and validate that the dc‐bus can be reconfigured in 100 ms, without torque interruption. [ABSTRACT FROM AUTHOR]

In a typical inverter-fed AC drive system, the stator windings carry a current with a large harmonics content, resulting in an increased AC loss. In this paper, the additional copper losses caused by non-sinusoidal currents are investigated for different magnet wire topologies, including the flat conductor, stranded, and litz wires. Also, a two-slot simplified model is introduced for accurate prediction of the AC losses at high frequency. It is found that one of the major issues of the conventional copper coil is that the losses are not uniformly distributed across the slot, and over 70% of the losses are concentrated near the slot opening. Moreover, using the transient finite element method, different winding topologies and arrangements are simulated at the stranded level to evaluate the losses and current density for each strand under highly distorted currents. Furthermore, different coil samples are prototyped for the same slot geometries to compare their performance under the same pulse-width modulation (PWM) waveforms for a wide range of frequencies. Finally, new hybrid coil topologies are proposed, which employ different magnet wires or materials within the same slot. The results demonstrate that utilizing a mixed wire configuration can effectively mitigate the adverse effects of eddy current losses. This approach can yield up to 16–41% lower losses while also achieving a weight savings of 36–70%. [ABSTRACT FROM AUTHOR]

Multiphase drives have received a lot of interest because of their several features over traditional three-phase systems for high-power applications. Pulse-width modulation (PWM) approaches are necessary to regulate the supply for multiphase ac drives. As a result, it is vital to continually improve the modulation and control approaches used to upgrade output power converters' quality. This paper offers a comparative analysis of the 2L + 2M and 6L space vector pulse-width modulation (SVPWM) techniques applied to a five-phase two-level voltage source inverter (VSI) fed an inductive (R-L) load. The comparative evaluation is based on measuring the inverter switching losses, the total harmonic distortion (THD) values, and the common mode voltage (CMV) under different operation scenarios. A system model is carried out by MATLAB/Simulink. An experimental prototype is constructed in the lab to validate the theoretical analysis. Simulation results for the system based on the two SVPWM techniques are obtained at different modulation indices and different output frequencies and are confirmed by the experimental results. It has been found that the peak-to-peak CMV of the 6L method is 80% lower than that of the 2L + 2M method. Moreover, 6L SVPWM offers better DC-link utilization compared to 2L + 2M SVPWM. [ABSTRACT FROM AUTHOR]

The rapid evolution of electric machines requires innovative approaches to boost performance, efficiency, and sustainability. Additive Manufacturing (AM) has emerged as a transformative technique, reshaping the landscape of electric machine components, ranging from magnetic materials to windings and extending to thermal management. In the area of magnetic materials, AM's capacity to fabricate intricate structures optimizes magnetic flux dynamics, yielding advanced shape-profile cores and self-coating laminations for superior performance. In windings, AM's prowess is evident through innovative concepts, effectively mitigating AC conduction effects while reducing weight. Furthermore, AM revolutionizes thermal management, as exemplified by 3D-printed ceramic heat exchangers, intricate cooling channels, and novel housing designs, all contributing to enhanced thermal efficiency and power density. The integration of AM not only transcends conventional manufacturing constraints but also promises to usher in an era of unprecedented electric machine innovation, addressing the intricate interplay of magnetic, winding, and thermal dynamics. [ABSTRACT FROM AUTHOR]

Switched reluctance machines (SRMs) are potential candidates for use in the propulsion systems of electric vehicles. However, they suffer from low power density and high torque ripple. In this paper, a segmented rotor double-sided axial flux SRM (DSAFSRM) is chosen for detailed analysis. A hybrid design algorithm is proposed to take the effects of iron non-linearity into account. The proposed design procedure benefits from simplicity and high accuracy at the same time. A two-step optimization procedure is presented which minimizes the torque ripple of the DSAFSRM without jeopardizing its efficiency. The torque ripple is reduced from 120% to 35% after optimization. In the two-step optimization procedure, both geometrical and switching related parameters are investigated. Moreover, a double-sided radial flux SRM is designed and compared with the proposed DSAFSRM in terms of torque ripple, average torque, efficiency and power density. The results indicate superior performance of the optimized DSAFSRM, especially in terms of average torque, which is 26% higher than the torque produced by the double-sided radial flux SRM. [ABSTRACT FROM AUTHOR]

This paper introduces a mathematical design and analysis of three-phase inverters used in electric drive applications such as aerospace, electric vehicles, and pumping applications. Different wide bandgap (WBG) semiconductor technologies are considered in this analysis. Using SiC MOSFETs and Si IGBTs, two drive systems are developed in order to show the improvement in the efficiency of the inverter. The efficiency, total losses of the drive systems and the power losses of two inverters are computed and compared for both drive systems at the same operating condition. The drive system with SiC MOSFET shows much better performance compared to the drive system with Si IGBT. The SiC MOSFET system provides a 59.39%, 86.13%, and 29.76% lower conduction losses, switching losses and drive's total losses, respectively, compared to the Si IGBT system. The efficiency of the SiC MOSFET system is 2.46%pu higher than the efficiency of the Si IGBT drive system. Moreover, this paper introduces a detailed analysis for the dc-link voltage and current ripples in three-phase inverters. Furthermore, the minimal dc-link capacitor needed to deal with the ripple current and voltage is investigated. Finally, the performance of the drive with Si IGBT is experimentally tested under different operating speeds and loads. [ABSTRACT FROM AUTHOR]

The reliability assessment of electric machines plays a very critical role in today's engineering world. The reliability assessment requires a good understanding of electric motors and their root causes. Electric machines mostly fail due to mechanical problems and bearing damage is the main source of this. The bearings can be damaged by mechanical, electrical, and thermal stresses. Among all stresses, the researcher should give special attention to the electrical one, which is bearing current and shaft voltage. This review paper introduces a comprehensive study of bearing current and shaft voltage for inverter-fed electric machines. This study aims to discuss several motor failure processes, as well as the sources and definitions of bearing current and shaft voltage. The different kinds of bearing currents are addressed and the parasitic capacitances, which are the key component to describe bearing current, are determined. Several measurement approaches of bearing current will be discussed. Furthermore, modeling of bearing current will be covered together with the machine's parasitic capacitances. Moreover, the different bearing current mitigation techniques, as described in many papers, will be thoroughly addressed. The use of rewound multiphase machines for mitigation of bearing current will be proposed and compared to a three-phase machine. Finally, various pulse width modulation techniques of multiphase systems that reduce bearing current and shaft voltage will be investigated, and the findings described in the literature will be summarized for all techniques. [ABSTRACT FROM AUTHOR]

This article presents the dynamic modeling and analysis of an electric motor with integrated magnetic spring (EMMS) when it is coupled to a weaving loom application. The EMMS can provide the majority part of the oscillating part of the load in a passive way by the magnetic spring. The electric motor provides the average torque and the remaining oscillating part in an active way. This reduces the energy consumption. To create an accurate dynamic model for the EMMS, lookup tables are generated from a finite-element model. Further, a 4-bar linkage mechanism is employed to emulate the behavior of the shedding mechanism of a real weaving loom application. Eventually, the whole system dynamic model was created in Matlab environment. Moreover, a complete experimental setup was constructed to validate the effectiveness of the proposed dynamic model and the EMMS behavior. It is shown that the proposed dynamic model effectively predicts the performance of the EMMS system. Besides, it is proved that the EMMS can effectively reduce the energy consumption of the weaving loom application. The amount of reduction in the energy consumption depends on the designed magnetic spring. For the considered application, it can reach 57%. [ABSTRACT FROM AUTHOR]

Recent advances in electrical machines and energy storage technologies make electric vehicles (EVs) feasible replacements to conventional internal combustion engines. One of the main challenges of high speed electrical machines is providing maximum output power with minimum energy losses, weight, and volume. At high frequency operation, the conductors of AC electrical machines can suffer from skin and proximity effects. This results in high AC losses in the machine windings and can eventually lead to machine failure. In this paper, a novel design for a semi-stranded coil is proposed to limit these undesirable effects. Enabled by additive manufacturing (AM) technology, this sophisticated design is 3D printed using ultralight aluminum alloy. Finally, the AC performance of this coil is measured and compared with conventional single-strand copper coil at different frequency levels. It is found that the proposed design can effectively limit the eddy current losses in the high frequency domain. [ABSTRACT FROM AUTHOR]

A modular motor drive (MMD) is composed of multiple identical pole drive units (PDUs), which consist of a concentrated stator winding fed by a dedicated power electronic converter module. To exploit the full flexibility and reliability of these MMDs, they are equipped with multiple controllers, operating as synchronized peers, and each driving only a limited set of PDUs. An MMD can hence be considered as a multiagent system, in which all the agents cooperate to deliver a certain torque demand. The goal of this work is to distribute this torque demand among the agents of a modular drive in a completely decentralized way, in order to comply with the flexibility and reliability of the hardware, while still taking into account the present condition of each agent. A deterministic consensus algorithm is used for this purpose, in combination with decentralized proportional integral (PI) current controllers. Communication is only allowed between neighboring agents, to limit the communication load. It is shown in this article that the total torque demand is delivered, under healthy conditions as well as during agent malfunctions and with nonidentical agents. The concept is demonstrated on a modular axial-flux permanent magnet synchronous machine with 15 PDUs that are assigned to five agents. [ABSTRACT FROM AUTHOR]

Powered prosthesis actuation is a field where energy efficiency and mass are important characteristics. The motion requirements of high torque at low speed and low torque at high speed are difficult to effectively combine in a single electric motor. A possibility is to use an oversized direct–drive motor that can deliver the peak torque. However, this results in a heavy actuation system and low overall efficiency. A common practice is combining a smaller electric motor with a gear reduction system. In the literature, novel redundant electric actuation systems have been presented with or without locking mechanisms to mitigate this problem. In this work, we provide a comparison of multiple electrical actuation systems composed of electric motors, gear reduction systems and locking mechanisms. This is done using the gait cycle of a human ankle as a case study. An electric motor with a double stator and a single rotor combined with a gearbox shows the most promising overall results when taking energy loss, total mass and complexity of the system into account. [ABSTRACT FROM AUTHOR]

Welding has a severe impact on the efficiency of electrical machines. The heat added during the welding process affects the microstructure of the material and causes residual stress. This results in local degradation of the magnetic permeability and facilitates additional iron losses in the machine core. With the purpose of modeling and simulating welding effects in electric machines, this paper proposes a stress-dependent magnetic equivalent circuit (MEC) model for welded non-grain-oriented electrical steel laminations. A modified iron loss model is proposed to accommodate these welding effects. Furthermore, the proposed MEC model is applied to a M270-35A stator core as a case study. It was demonstrated that the core losses increase by 25% when four welding joints are applied. With a limited number of magnetic measurements on a welded and unwelded core, the model can be fully parametrized. Finally, the model was successfully validated on a core with eight welding seams at 100 Hz. The proposed model can be integrated into the design of electric machines to consider the welding effects. [ABSTRACT FROM AUTHOR]

Thanks to the absence of rotor windings and permanent magnets, switched reluctance motors have a small weight construction. The integration of a modular power converter in a switched reluctance motor leads to a highly compact and fault-tolerant motor drive with small weight and high power density. In this article, a polygon-retrofitted integration topology is proposed for switched reluctance motors. Both the switched reluctance motor and the power converter are cooled with one shared cooling circuit. The power converter is designed and implemented using silicon carbide technology for its low losses and small thermal resistance. The proposed integration topology is extensively studied using multiphysics modeling and experimental measurements on a fully integrated rotating setup. A highly compact and power dense drive of 3.1 kW/L is obtained. [ABSTRACT FROM AUTHOR]

Due to the significant advantages of a high torque density, better fault tolerance and high efficiency, the combined star–pentagon winding has recently gained researchers' interest. In this paper, a simple method to identify the sequence of phases of a five-phase machine with combined star–pentagon winding was proposed. This was accomplished using resistance measurements between adjacent and non-adjacent phases. The analysis was conducted to clarify the phase sequence identification method. A case study of a 5.5 kW five-phase synchronous reluctance motor with combined star–pentagon winding was considered to simply apply the proposed method using an LCR meter for resistance measurements. The parasitic and wire resistances are dominant in the studied case, and this did not influence the accuracy of this method. [ABSTRACT FROM AUTHOR]

Although it is well known that the magnetic properties of electrical steel can be deeply affected by the cutting process, it is still not clear how to accurately evaluate these effects on a prototyped machine on its final shape, especially at a high frequency or a high power rating. This research provides a more practical method for accurate measurement of magnetic losses in electrical steel with consideration of material degradation effects due to the cutting process. Unlike other similar studies, these investigations are conducted not only on a few laminations but also on a complete electrical machine core. For a fair comparison between both cases, backlack bonding is used for lamination stacking since it is the most non-damaging joining technique. Two different test setups are used to measure the steel performance at a wide range of frequency and input power. Furthermore, a full axial length stator of a switched reluctance machine (SRM) is used as a case study to identify the magnetic properties of NO20 electrical steel. Additionally, by comparing the results obtained from the individual laminations and the assembled stator, the extra losses due to the cutting process and material degradation are extracted accurately. [ABSTRACT FROM AUTHOR]

In this work, a proposed high-efficiency and low-cost photovoltaic water-pumping system based on semitransparent dye-sensitized solar cells (DSSCs) is presented. DSSCs are low-cost third-generation photovoltaics that have gained a lot of interest as a promising alternative for silicon solar cells. DSSCs are fabricated at low cost and low temperature and present power conversions with high efficiency, exceeding 14%, thanks to high transparency, a variety of colors, and high efficiency, even in low light conditions. The DSSC modules used in this study were tested under different working conditions, and their characteristics were determined experimentally and simulated theoretically via MATLAB. A complete laboratory infrastructure is constructed to test the proposed photovoltaic water-pumping system based on the DSSC module array. The system contains a synchronous reluctance motor driving a water pump and feeding from the DSSCs via an inverter without DC–DC converters or batteries. The proposed system has many merits, such as high efficiency and low cost. The DSSCs' maximum available power is obtained via a maximum power point tracking technique (perturb-and-observe). Moreover, a control system for driving the motor via the inverter was also implemented. The maximum torque per ampere strategy is also considered in the proposed control system to drive the motor efficiently using the inverter. Finally, experimental validation of the complete system via laboratory measurements is implemented. [ABSTRACT FROM AUTHOR]

This paper investigated and demonstrated an electric drive topology with inherently high reliability and improved performance. The topology combines a five-phase combined star-pentagon synchronous reluctance machine (SynRM) and a power electronic "matrix" converter without vulnerable electrolytic capacitors, which are often a point of failure of conventional drives. This drive is suitable for harsh environments, with possibly high ambient temperatures and limited maintenance. In this paper, an accurate model of the five-phase combined star-pentagon SynRM was introduced considering the effect of magnetic saturation and cross saturation on dq-flux-linkages. The five-phase combined star-pentagon SynRM will be connected to a three-to-five-phase indirect matrix converter (IMC) and the indirect field-oriented control based on a space vector pulse width modulation was applied. The introduced SVM commutates the bidirectional switches of the IMC at zero current which enhance and minimize the switching losses. The performance of the proposed drive system was studied and experimentally validated at different loading conditions. Finally, the reliability, cost, and performance of the proposed drive system were compared with the conventional drive system (three-phase star-connected SynRM fed from rectifier-inverter). [ABSTRACT FROM AUTHOR]

The electric drive power density and fault tolerance capability are of fundamental importance in many applications such as aerospace and traction applications. The modularization and the physical integration of the electric motor and the power converter components can lead to a high power density and a high fault tolerance drive system. The power density of a highly modular and integrated drive based on an axial flux permanent magnet synchronous machine and GaN converter is investigated in this paper. Several power density boosting techniques are provided and investigated using CFD simulations. These techniques incorporate optimization of the converter topology, the geometry of the shared cooling structure of the electric machine and the power converter and optimal selection of the materials in the path of heat transfer from the machine and the power converter to the cooling ambient. The power density of the reference integrated design is increased from 1.12 kW/ $l$ to 2.14 kW/ $l$. The CFD computations are validated by extensive measurements on a modular integrated setup. [ABSTRACT FROM AUTHOR]

This paper introduces and analyzes the power losses of a five-phase drive system based on an indirect matrix converter (IMC) and a five-phase synchronous reluctance motor (SynRM). The different loss components in the power converter and the motor have been discussed and analyzed. Moreover, a control strategy is applied to decrease the power converter losses and make the system superior to the conventional one. The carrier-based pulse-width-modulation (CBPWM) method is used for this. Through the CBPWM, switching losses are kept as low as possible in this technique by ensuring that the rectifier stage experiences zero current commutation. To achieve this, the rectifier and inverter stages are synchronized so that the commutation in the rectifier stage occurs at the zero vectors of the inverter, which corresponds to a zero DC-link current. The converter will therefore have less switching losses thanks to the rectifier's null value. Experimental validation has shown the usefulness of the proposed CBPWM in providing lower switching losses in the IMC. Additionally, a comparison of the proposed drive system's performance with a traditional three-phase SynRM-based inverter will be carried out in the speed and torque control modes. [ABSTRACT FROM AUTHOR]

In this article, a circulating-current-excited switched reluctance generator system using a standard diode rectifier is proposed and examined. It features a dc power source connected in series with the ring-connected windings, which provides the dc-bias current as the excitation current in the windings. Using a series-connected dc power source, a dc-bias current is easily realized in the ac winding. Compared with the existing machine having dc-bias in the ac winding, the proposed generator can provide dc power with a standard diode rectifier. Less active legs and no rotor position sensor are needed for the control of the circulating current of the proposed generator, which increases the reliability of the generation system. The system configuration and the operation principle are introduced in detail. Then, the electromagnetic performance of the proposed generation system is analyzed at both open-circuit and load conditions. The asymmetric current distributions are deduced and verified by the simulations. At last, the prototype is tested under varied operation conditions and the experiments agree well with the analysis. [ABSTRACT FROM AUTHOR]